Elastomeric monolithic drywall corner

ABSTRACT

A room having a monolithic wall surface throughout formed from gypsum wallboards, with perpendicularly disposed walls made monolithic by an elongate, concave, elastomeric bead formed in situ, with feathered edges flush with the adjacent wallboards.

United States Patent Schneller et al.

1 Aug. 28, 1973 ELASTOMERIC MONOLITHIC DRYWALL CORNER inventors: Joseph W. Schneller,Wi1liamsvil1e;

Richard E. Smith, Tonawanda,

both of N.Y.

Assignee: 'Naiimeypmicbm'paay;

Buffalo, N.Y.

Filed: Aug. 6, 1971 Appl. No.: 169,733

US. Cl 52/287, 52/309, 52/415,

156/71 Int. Cl E041) 2/10 Field of Search 52/287, 288, 415,

[56] References (Iited UNITED STATES PATENTS 3,350,825 11/1967 Rillo 52/746 X 2,078,049 4/1937 Benedict 52/417 2,902,855 9/1959 Stoll 15/23$.7

3,444,657 5/1969 Swanson 52/288 3,576,091 4/1971 Shull et al 52/417 X Primary Examiner-Price C. Faw, Jr. Attorney-Robert F. Hause ABSTRACT A room having a monolithic wall surface throughout formed from gypsum wallboards, with perpendicularly disposed walls made monolithic by an elongate, concave, elastomeric bead formed in situ, with feathered edges flush with the adjacent wallboards.

3 Claims, 6 Drawing Figures Patented Aug. 28, 1973 3,754,363

2 Sheets-Sheet l INVENTO 5 Joseph W. Sch nel er By Richard E. Smith ATTORNEY Patented Aug. 28, 1973 3,754,363

2 Sheets-Sheet 2 Fig. 6 Fig. 4

INVENTORS Joseph W. SchneHer BY icho rd E. SmHh Fig. 5 ATTORNEY ELASTOMERlC MONOLHTHIC DRYWALL CORNER This invention relates to concealing the joint between abutting gypsum wallboards at an inside comer.

The most common form of interior walls, for many years, has been drywall, which consists of papercovered gypsum wallboards, with a joint-concealing system, which results in a monolithic wall. The jointconcealing system has, for years, been almost universally a thin paper tape adhered over the joint with a cementitious adhesive referred to as joint compound, which, after drying, is covered with another layer of joint compound, dried again and then one or two more coats of joint compound. Such joint-concealing systems have been commonly used on flat joints and on inside corner joints.

it is the above-mentioned inside corner joints to which this invention relates. A simple treatment, with one component, which can be applied without delays for drying, which requires very little time in application, and which almost immediately after application can be painted and thus completed, is clearly desired.

it is an object of this invention to provide an improved drywall inside corner. It is a further object to provide a novel method of concealing the joint of paper-covered gypsum boards at an inside corner. It is a further object to provide a concealed drywall inside corner which is rapidly formed, aesthetically appealing, immediately capable of decorating, and strong and resistant to cracking or other destructive forces.

These and other objects and advantages of the invention will become readily apparent from the following description and the drawings in which:

H6. 1 is an isometric view of a room with a monolithic wall surface formed from gypsum wallboards in accordance with the invention.

FIG. 2 is an isometric view of two perpendicularly disposed gypsum wallboards with a rough bead of an elastomer-forrning compound being applied at the inside corner.

FIG. 3 is a view similar to H6. 2 subsequent to the partial conversion of the rough bead to a concave bead.

HO. 4 is a front view of the tool for forming a concave bead.

FIG. 5 is a side view of the tool of HG. Al.

FIG. 6 is an end view of the tool of FIG. 4.

Referring to FIG. ii there is shown in a cutaway view the interior of a room 10 having a single monolithic wall 12 which is constructed from a plurality of gypsum wallboards i4, 14, each of which is affixed to wooden studs 16, forming the wall framework. Aside from doors 1% and windows 20, it will be noted that monolithic wall 12 is essentially one continuous unbroken surface, with joints between adjacent wallborads E4, 14 being concealed.

in particular, the joint at inside corner 22, between wallboards 14a and Nb is concealed in a novel manner in accordance with the present invention.

Referring to FIG. 2, there is shown the two gypsum wallboards 14-0, 14b during construction, disposed in perpendicular relationship forming inside corner 22, within which there is being adhered, to the two boards 14a, 14b, a rough head 2 of a potentially elastomeric compound, applied thereat by a caulking gun 26. The size of the rough bead is controlled by the size of the opening at tip 28 of gun 26S, and by the velocity at which the gun 26 is advanced along the length of corner 22. With practice, the size of bead 2 can be kept just sufficient to provide the amount of material to produce a concave bead of the desired size, in accordance with the invention.

Substantially immediately after the gun 26 had deposited bead 24 of elastomer-forming compound in corner 22, the rough bead 24 is deformed into a concave bead Ml. Preferably a tool 32 is used to convert rough bead 2d into concave bead 30. Tool 32 is particularly advantageous in forming concave bead 30 on gypsum wallboard corners, however it may be used with many other board, tile or panel corners, also. Tool 32 is the subject of a copending patent application of Joseph W. Schneller Ser. No. 169,726 also filed Aug. 6, 197i.

Concave bead 334i may also be formed in gypsum board inside corners by means other than tool 32, such as by an individual finger tip or by a pencil eraser. Regardless oi the means used, a highly advantageous drywall corner is provided by the concave elastomeric bead formed.

The preferred tool 32 has a basically square rubber head 3%., of about 1% inches square, of about oneeighth inch thickness and of about shore A durome ter hardness. One corner 36 of the head 34 is affixed within a slot in a handle 3%, with more than half of the diagonal extent disposed within the slot. The beadforming corner 43th, opposite comer 36, is formed with a radius approximately equal to the radius desired for the concave head 3% such as about one-eighth inch. The edge of the head at the corner M) and along the two sides 42, 412 of the head adjacent corner 40 are rounded in a 1/16 inch radius.

The elastomer-t'orming compound of the present invention is preferably a composition consisting primarily of an acrylic latex emulsion and ultra fine inorganic extender, such as fine calcium carbonate. Various other additives may be included in minor quantities as is well known in the art of forming thickened e -astomerforming compositions, including plasticizers, p eservatives, pigments and solvents, however the critical elements of the present invention are not particular ingredients, but instead are particular product characteristics which have been found to provide the novel results of the invention.

The elastomer-forming compound is suitable for storage in sealed containers for a year or two before use without substantial degradation.

The elastomer-forming compound has a viscosity or consistency and an adhesion to wallboard paper such that there is no sag when a rough bead of about .1 square inch cross-sectional area is deposited on a vertically disposed flat surface of gypsum wallboard paper. Removal of the bead after drying for 24 hours results in removal of a surface portion of the paper.

The elastomer-forming compound has a period of workability of about ten minutes, in which time the rough head can be easily converted to a concave feathered bead with a smooth surface, with a suitable rounded end tool.

The elastomer-forrning compound has a skinning effect such that the surface loses all tackiness in from 10 to 30 minutes and is paintable in 68 minutes. This makes possible the highly advantageous process of painting the same day, that is, within about 24 hours.

The elastomer-forming compound of the invention has the characteristic, after drying for about 48 hours, of developing an elastomeric form which can be stretched 50 percent and which will then return about 75 percent of the way back to its original length, when testing a six inch length having a inch by /4 inch cross section.

Finally, the elastomer-forming compound produces an elastomer, on drying, which is inert relative to interior wall paints, but is receptive to adhesion of the paint to the concave bead surface.

An acrylic latex based Macco adhesive No. 005, produced by SCM Corporation, provides, to a substantial extent, the essential characteristics defined hereabove for the elastomer-forming compound of the invention. The Macco adhesive consists of about the following:

Acrylic latex emulsion (55% solids) 45-50% Inorganic extender 4S50% Plasticizer l5% Preservative 1% Another, more expensive, compound that was able, to a substantial extent, to provide the essential characteristics defined above had, as a binder, a mercaptan in place of the acrylic.

The concave head 30 can be any of a wide range of sizes. Relatively small size beads, of about one-eighth inch radius, are preferred, however when the wallboard corner is formed with gaps between the boards, as is common, the radius of concavity of the bead will have to be at least about two times the width of such gaps.

Preferably the gaps should be no bigger than about one-half inch with a concave bead radius of about one inch. Gaps of about one-quarter inch or more should be filled with one of the known prior types of settable drywall joint compounds, which is allowed to set prior to forming the concave bead.

The corner head 30 has a final cross section which may be described as identical in shape to one of the four corner pieces removed when a circle of a given diameter is cut out of a square with sides equal to the circle diameter. The comer bead 30 has an exposed arcuate surface 50 with two respective edges 52 which are tangential to the two respective hidden back surfaces 54. Back surfaces 54 are firmly adhered to the wallboard paper, and accordingly arcuate surface 50 is tangential also to the surface of the two respective gypsum wallboards.

The caulking gun used in applying the rough bead 24 to the inside corner 22 may be any of many available types of gun, including hand actuated or power actuated, such as air powered.

As can be noted in the drawings, the room of the invention has inside corners 22 which, by reason of the invention, provide a novel monolithic effect, with a very minimum of material and labor.

The novel inside drywall corners 22 are capable of withstanding relative movements of wallboards l4, 14 of 0.080 inch without any noticeable efi'ect on the finished monolithic appearance of the corner, whereas with the common prior method of finishing drywall corner joints, with conventional paper joint tape and cementitious binder, a maximum tolerable deformation was about 0.025 inch. This ability to withstand movements is particularly important with the present increase in prefabricated modular housing with its increase in amounts of stress and strain.

The resistance to movement stresses is also highly advantageous in conventional on-site construction, wherein hygroscopic movement of the wall elements occurs and has in the past often resulted in objectionable cracks forrning at corners. The hygroscopic movement results from absorption or loss of water from wood studs or from the gypsum wallboard, which is formed from a set gypsum core between front and back paper facings.

The respective wallboards at a comer treated in accordance with the invention may be on two adjacent vertical walls or on an adjacent ceiling and a vertical wall, and thus wall is intended to mean a ceiling or a vertical wall.

Having completed a detailed disclosure of the preferred embodiments of our invention, so that others may practice the same, we contemplate that variations may be made without departing from the essence of the invention or the scope of the appended claims.

We claim:

1. A drywall structure comprising at least two walls and an inside comer therebetween, said walls having a surface formed of gypsum wallboards, said gypsum wallboards having a set gypsum core between front and back paper facings, said corner being formed by pairs of gypsum wallboards having front paper facings of the respective gypsum wallboards disposed at an angle one to the other forming said inside comer and with a spacing therebetween of no more than about one-half inch, and an elastomeric concave comer bead adhered to both respective gypsum wallboards, said comer bead and gypsum wallboards having, in cross section, an arcuate surface of said corner bead with respective side edges with are tangential with the respective front surfaces of said gypsum wallboards, said elastomeric concave corner bead being formed from a mixture com prising a latex emulsion and ultra fine inorganic extender.

2. A drywall structure as defined in claim 1 wherein said latex emulsion is an acrylic latex emulsion.

3. A drywall structure comprising at least two walls and an inside comer therebetween, said walls having a surface formed of gypsum wallboards, said gypsum wallboards having a set gypsum core between front and back paper facings, said comer being formed by pairs of gypsum wallboards having front paper facings of the respective gypsum wallboards disposed at an angle one to the other forming said inside comer and with a spacing therebetween of no more than about one-half inch, and an elastomeric concave comer bead adhered to both respective gypsum wallboards, said comer bead and gypsum wallboards having, in cross section, an ar cuate surface of said comer bead with respective side edges which are tangential with the respective front surfaces of said gypsum wallboards, said elastomeric concave comer bead being formed from a mixture of a mercaptan binder and ultra fine inorganic extender. K 3 

1. A drywall structure comprising at least two walls and an inside corner therebetween, said walls having a surface formed of gypsum wallboards, said gypsum wallboards having a set gypsum core between front and back paper facings, saId corner being formed by pairs of gypsum wallboards having front paper facings of the respective gypsum wallboards disposed at an angle one to the other forming said inside corner and with a spacing therebetween of no more than about one-half inch, and an elastomeric concave corner bead adhered to both respective gypsum wallboards, said corner bead and gypsum wallboards having, in cross section, an arcuate surface of said corner bead with respective side edges with are tangential with the respective front surfaces of said gypsum wallboards, said elastomeric concave corner bead being formed from a mixture comprising a latex emulsion and ultra fine inorganic extender.
 2. A drywall structure as defined in claim 1 wherein said latex emulsion is an acrylic latex emulsion.
 3. A drywall structure comprising at least two walls and an inside corner therebetween, said walls having a surface formed of gypsum wallboards, said gypsum wallboards having a set gypsum core between front and back paper facings, said corner being formed by pairs of gypsum wallboards having front paper facings of the respective gypsum wallboards disposed at an angle one to the other forming said inside corner and with a spacing therebetween of no more than about one-half inch, and an elastomeric concave corner bead adhered to both respective gypsum wallboards, said corner bead and gypsum wallboards having, in cross section, an arcuate surface of said corner bead with respective side edges which are tangential with the respective front surfaces of said gypsum wallboards, said elastomeric concave corner bead being formed from a mixture of a mercaptan binder and ultra fine inorganic extender. 